Some dinosaurs cooed rather than roared.
Fossils can give us detailed insights into what extinct dinosaurs were like, but some things — sounds, for instance — just don’t fossilize.
Writing in the journal Evolution, a group of researchers has turned to living dinosaurs, i.e. birds, to gage how dinosaurs of the past might have vocalized.
Most birds make noise with an open beak, but some can produce sounds with closed mouths by pushing air into a specialized vocal organ in their neck. These closed-mouth vocalizations are quiet, low-pitched, and often used to attract mates or defend territories. Dove cooing and the mating calls of ostriches are prime examples.
Closed-mouth ostrich mating call.
The researchers examined how closed-mouth vocal behavior is distributed across modern birds and closely related reptiles, and then used a statistical approach to reconstruct where this behavior first emerged in ancestral species.
"Our results show that closed-mouth vocalization has evolved at least 16 times in archosaurs, a group that includes birds, dinosaurs and crocodiles,” said study co-author Chad Eliason, from The University of Texas Jackson School of Geosciences, in a press release.
It is predominantly large-bodied species (the size of a dove or larger) that make sounds this way, likely because small species have a limited capacity to inflate their lungs.
Given that extinct dinosaurs were members of the archosaur group, and many had massive body size, the researchers believe “that the capacity for closed-mouth vocalization was present in at least some extinct nonavian dinosaurs.”
Closed-mouthed noises are a far cry from the resounding roars that one might expect from a large dinosaur.
"This makes for a very different Jurassic world,” commented study co-author Julia Clarke. “Not only were dinosaurs feathered, but they may have had bulging necks and made booming, closed-mouth sounds."